Diclofenac phonophoresis in human volunteers

A quantitative study of sodium diclofenac (Voltaren Emulgel, Novartis) phonophoresis was undertaken in humans. Fourteen healthy human volunteers were submitted to ultrasound irradiation on two 225-cm2 areas on the dorsum (group A), followed by the application of the medication gel, and the plasma diclofenac mass was measured at 1, 2 and 3 h later by high performance liquid chromatography. The same procedure was repeated one month later with the same volunteers but with the ultrasound equipment switched off for the control group (group B). The plasma diclofenac mass was significantly higher in group A than in group B at 1 h (0.0987 microg/mL as opposed to 0.0389 microg/mL; p=0.01) and 2 h (0.0724 microg/mL as opposed to 0.0529 microg/mL; p=0.01), but not at 3 h (0.0864 microg/mL as opposed to 0.0683 microg/mL; p=0.16). The authors conclude that previously applied therapeutic ultrasound irradiation enhances the percutaneous penetration of the topical diclofenac gel, although the mechanism remains unclear.